Stephen B. Hamilton, Jr., in U.S. Pat. No. 3,446,856, first discloses a method for methylating the ortho position of phenol by the vapor phase reaction of phenol with methanol in the presence of magnesium oxide as a catalyst at a temperature ranging from 475.degree. to 600.degree. C., in which the service life of said catalyst at the typical reaction temperature of about 530.degree. C. is about 90 to 100 hours, and the catalyst is pure magnesium oxide in powdered or sintered form which causes processing difficulties due to its weak mechanical properties.
Van Sorge has developed several improved catalysts for the same ortho-alkylation process as disclosed by above mentioned U.S. patent, which comprises bonding magnesium oxide with suitable materials. In his inventions of U.S. Pat. Nos. 3,843,606, 3,974,229, and 4,097,411, an inert organic polymer, manganese oxide, and silica are disclosed as a binder respectively. The bonded catalysts taught by Van Sorge, which may be molded to any desired shape, generally have the following improvements such as excellent physical properties, a service life of many hundred hours, a catalyst bed temperature varying between 460.degree. and 500.degree. C., and a higher degree of selectivity and yield.
Kong R. Chang and one of the inventors of present invention, Trong G. Lin in U.S. Pat. No. 4,546,093 disclosed a process for preparing 3-component catalyst system consisting of manganic oxide, ferric oxide and zinc oxide, which is used for the catalytic synthesis of 2,6-xylenol from reacting phenol with methanol. This 3-component catalyst has an improved reaction activity and selectivity with comparison to the magnesium oxide catalyst taught by Van Sorge. However, the present invention further provides a process to promote this 3-component catalyst.
In co-pending application Ser. No. 07/206,834 filed in 1988, the inventors of present invention with co-inventors disclosed a catalyst for ortho-alkylation of phenols which is prepared by calcining a co-precipitate of magnesium salt and manganese salt. Furthermore, they taught that an additional alkali metal oxide may be formed on the surface of the alkylation catalyst to enhance its service life.